Fluid Directions - Full Hydraulic Steering Basics

Steering is one of the two most important systems on your vehicle (the other being brakes). Finding the perfect steering system for your four-wheeler is vital to making it perform off-road. In the last 10 years full hydraulic steering has taken the off-road world by storm, but it’s nothing new. Tractors have been running hydraulic steering for ages and with good reason: They must turn in rough terrain, and the equipment must be simple and easy to fix.

Hydraulic steering (or what we refer to as full hydro) is different from a standard steering gearbox, or rack-and-pinion, in that there is no mechanical connection between the steering wheel and the actual wheels. Instead of having a steering box it has a steering valve. When the steering wheel is moved a valve opens and closes. The valve sends pressurized hydraulic fluid to either end of a hydraulic ram. The ram forces the wheels to turn whichever direction you turned the wheel. Thus the fluid inside the hoses is the only connection between the steering wheel and the steered wheel.

The long feed hose was starving the pump

For this reason we do not recommend using hydraulic steering on a street-driven vehicle. And we also must emphasize that even though we call it full hydro, you do not want to use hydraulic fluid, but rather stick with real power steering fluid. If you were to have a failure in the hydraulic hoses you could lose your steering and results could be disastrous. As you may have noticed, there are not a lot of tractors running down the highway at high speeds, nor production sports cars and trucks running full hydraulic steering. We’ve seen it done and we’ve tried it, and we just don’t recommend it.

Tractors have used hydraulic rams to steer for a long time. These agriculture-based systems often have huge hydraulic reservoirs and also use the hydraulic fluid for running other equipment such as front-end loaders, rear three-point hitches, or towed machinery. These systems have massive integrated pumps designed for the job and multigallon reservoirs, but the basic tractor steering ram isn’t right for your 4x4 because they often lack the power needed for our massive tires.

So what makes hydraulic steering so great? Mainly it is the ability to build a suspension that is unencumbered by steering linkage such as a four-link. But also it is the fact that it is powerful for turning big tires and simple in that it doesn’t need a drag link to connect from a frame-mounted steering gearbox to the axle. You can build a trick steering system that will work with a four-link suspension, but it usually involves a more complex system of bell cranks and multiple drag links, which you can read about in Harry Wagner’s story “Linking Outside the Box” on page 68 in this issue.

We recently swapped our Fun Buggy over to full hydro steering in anticipation of a front four-link suspension conversion. We also looked at a few other full hydro steering systems and how they work as ideas for future projects.